1. Field of the Invention
The present invention relates to a process for the conditioning of contaminated waste through cementing. Dry waste is cemented, especially waste which is recovered as ashes subsequent to the combustion of burnable waste, or as a dry residue during the treatment of sludge.
2. Discussion of the Prior Art
It is known that weakly radioactive to medium radioactive waste materials which contain burnable components can be incinerated in combustion furnaces, and radioactive liquids concentrated through evaporation and the obtained sludge processed into a dry residue. Inasmuch as the radioactivity of weakly radioactive to medium radioactive waste materials will only decay within a longer period of time, it is a usual procedure to mix the dry waste with bitumen or cement and to insert it into metal drums. The portion of the dry waste in such cement drums is constituted of about 25% by weight.
Not only radioactive waste materials allow themselves to be encased through cementing. Also toxic waste, which does not permit itself to be further processed and which, due to its solubility in water, is not capable of being directly deposited, can be stored in this manner. The herein employed term "contaminated waste" includes such materials and other deleterious waste comparable therewith which is to be stored.
Of decisive significance in the cementing of contaminated wastes is, on the one hand, the leaching behavior of the compound member obtained subsequent to the setting and hardening of the cement upon contact thereof with water, and, on the other hand, its strength. Sought after is a lowest possible leaching rate for the compound member so that in the event, of an accident involving water ingress in the repository, no contaminated waste enclosed in the compound member can engress into the water. However, also the strength of the compound member, in particular its resistance to pressure and its surface hardness, may not fall below a minimum extent, in order to avoid any abrasion and, as a result, the release of contaminated waste into the environment.
The leaching behavior of the compond member depends to a considerable extent upon its porosity. However, the strength of the compound member is also influenced by the porosity. Consequently, it is an object to obtain the highest possible material density. It is also of significance that the volume which is to be introduced into the repositories for the storage of the contaminated wastes be maintained as small as possible, inasmuch as the space in natural ground which is available for the storage, for example, in salt deposits, is not available to an unlimited degree.